Hi there, my son has a 1998 Camaro (got it 2 months ago) with a 3.8L engine. It seems to have a misfire problem that we cannot figure out. The check engine light came on, so we had the code read. It came back as a "Cylinder 5 Misfire". We had planned on replacing the plugs any way, so we replaced all of the plugs and wires (Bosch 7mm). That apparently didn't resolve the problem. We took it a Chevy dealer and got the royal treatment, at least we think so. They said cylinders 5 & 6 had a misfire. They wanted $550 to perform a compression check, and injector flow balance check. Notice they didn't say they would fix anything, just check/diagnose the compression and injector flow balance. I'm sure the laundry list of what they find would have been into the thousands.

I decided to check the compression in the offending cylinder myself sinceI had a compression test tool. The compression quickly jumped up to 120 on the first crank, 150 on the second and 180 on the third. I intepreted that to mean the cylinder has great compression. I didn't check the remainding cylinders to se how they varied, but I'll do that at a later date. Since that seemed like it was OK, I then decided to check the ignition coil modules. The 2-5 coilmodule read low on the primary coil (.2 Ohms), and the 3-6 pack read high (1.2 Ohms) according to the Haynes manual (.3 - .6 Ohms). I replaced all three modules hoping that would fix it. At first I thought that fixed it, but as I drove it around, and it warmed up, the misfire was more obvious, especially when accelerating up a hill. I then pulled the plug and performed a spark test using a spark test tool. With the engine running, a clear strong spark was seen at the cylinder 5 plug wire. I bought my own code reader and once again, it read a Cylinder 5 misfire.

At this point, I'm at a loss as to what to do about the misfire. I guess I'll have to take it to a shop if I cannot get it figured out, but not to that dealership again. Any help or advice would be greatly appreciated.

Thanks in advance.

Jorden

 

Have you tested the ignition control module uder the coil packs? What does the #5 plug look like compared to the others?Also, No 5 injector may not be working properly. Misfire can be due to bad ignition, bad injectors, or engine damage.

 

Z28Pete,

Thanks for the reply. I didn't test the Ignition Control Module. I suppose between that and the injectors that's next on the list.

After clearing the code, I did test drive it again, and while the engine was cold/cool it pulled strong. No noticeable misfire, no check engine light. After about 5 minutes into the test drive, and about 6 miles, it started misfiring againg. Check engine light blinked a couple of times, and then stayed on. I put the code reader on, and now it tells me a misfire on cylinder 6. Very frustrating. I'm wondering if maybe it is the Ignition Control module, since Cylinders 5 and 6 are on different coil modules. Or maybe it could be vapor lock since it seems to be affecting the two rearmost cylinders.

It constantly pops and backfies through the glasspack muffler, kind of like it's running rich. I can't tell if that's because it's misfiring, the excess fuel is spontaneously or something else.

Thanks again

Jorden

 

What you are explaining sounds exactly like my problem I had a few feeks ago. I had the throttle body and injectors cleaned which solved the problem. Hope this helps!

 

It seems that your car starts to run bad once it goes into closed loop and the PCM starts using sensor data. You can force it back into open loop by pulling the plug from the MAF sensor. If it runs good with the MAF disconnected, there is a very good chance that a sensor is bad.

 

A quick and easy thing to try is add Lucas Upper Cylinder cleaner to your gas tank and it will clean your injectors -- using this quarterly will help your car, and I can notice improvements...

 

i had a similiar prob. kept getting the code for a #5cylnder misfire, changed plugs wires and coils...same thing..it ended up being the MAF sensor, bought one from autozone and it didnt work,got another one from autozone it didnt work...had to get it from the dealer and have had no problems outta it since then

 

Did you re-set the codes?

Try swaping the coil pack with another one. If the code moves to another cylinder, you've found the problem.

 

Desi,

The coil modules are brand new. Doesn't mean they can't be bad though. I'll try that.

Anyone,

Is there a way for me to clean the injectors and throttle body myself, or is cleaner in the tank, dealer/shop cleaning the only way(s).

Thanks.

Jorden

 

3M makes injector cleaners in aerosol cans. You should be able to pick them up from your local automotive stores.

Throttle body you can clean with carb cleaner....be very careful not to damage the sensor.